My dissertation uses medical film as a lens on the history of the mind sciences of the child. Through a close reading and historical contextualization of films and videos on infants and young children in Germany, France, Britain, and the USA from the early twentieth to the twenty-first century, the study explores how medical film has contributed to and shaped our understandings of the mind of the child, be it as a technology of observation in the early twentieth century or as a therapeutic tool in the late twentieth century. Drawing on recent approaches that intersect the history of science with art history, the study engages with three bodies of scholarship: the history of child psychiatry and psychology, the history of medical visualization, and the history and sociology of biomedicine. It contributes to the history of child psychiatry and psychology in using film as a window on common historical trends beyond disciplinary and national borders. It engages with the history of medical visualization in exploring epistemic differences of moving images to other methods of visualization (such as X-ray and MRT) and shedding fresh light on the status of images in twentieth century medical knowledge. Finally, it contributes to studies of biomedicine in investigating the role of video technology in present transformations of child psychiatric practices. My dissertation takes into account a large number of different contexts (historical, disciplinary, national) and will depend on intensive archival work on multiple sites (USA, Germany, France, Britain). Overall, it aims at contributing to a better understanding of the role of visual technologies in past and present of our knowledge of the mind of the child.